As this type of image sensor, there exist, for example, a CMOS (Complementary Metal Oxide Semiconductor) type solid-state image sensor for picking up images by converting incident light into voltages to generate and transfer voltages corresponding to the intensity of the light, and a CCD (Charge Coupled Device) type solid-state image sensor for converting incident light into electric charges to generate signal charges corresponding to the intensity of the light. The CCD type solid-state image sensor (hereinafter abbreviated as “CCD”) will be described by way of example. As shown in FIG. 15, an FT (Frame Transfer) mode provides photogates 111 arranged two-dimensionally, and storage CCD cells 112 likewise arranged two-dimensionally. Each photogate 111 is constructed as a photoelectric converter for converting incident light into electric charges to generate signal charges corresponding to the intensity of the light. Each storage CCD cell 112 is constructed as a charge transfer unit for successively transferring the signal charges vertically as seen in the drawing of FIG. 15 to store the charges in an adjoining cell.
Horizontal transfer CCD cells 113 are arranged as connected downstream of the storage CCD cells 112 for transferring the transferred signal charges horizontally as seen in the drawing of FIG. 15. These photogates 111, storage CCD cells 112 and horizontal transfer CCD cells 113 constitute an image pickup unit 114. Further, a plurality of coupling CCD cells 115 are connected in order downstream of the horizontal transfer CCD cells 113. A charge multiplier 116 is connected downstream of the coupling CCD cells 115 for multiplying the signal charges transferred from the horizontal transfer CCD cells 113 through the coupling CCD cells 115. And a charge-to-voltage converter 117 is connected to the charge multiplier 116 for converting the multiplied signal charges into voltages. The charge multiplier 116 generates, for example, a high electric field region for charge multiplication to multiply the signal charges by passage through the high electric field region when transferring the signal charges (see Patent documents 1 and 2, for example). These image pickup unit 114, charge multiplier 116 and charge-to-voltage converter 117 are formed on the same board 110.
[Patent Document 1]
Unexamined Patent Publication H7-176721 (pages 3-7, FIGS. 1-11)
[Patent Document 2]
Unexamined Patent Publication H10-304256 (pages 4-5, FIGS. 1-4)